ABSTRACT
This chapter addresses the issues of local, regional and national process by examining a particular type of rural social organization in southern Mexico: the irrigation associations, their expansion and use of new technologies as a response to demographic pressure and decreasing availability of irrigation water in the Tehuacan Valley, Mexico. Agriculturalists in arid and semi-arid areas strive, in the context of both subsistence and cash crop production, for control over the dual resources of land and water. In the arid Tehuacan Valley in South Central Mexico, agriculturalists have for centuries been using canal irrigation based on groundwater. The galerias are designed and constructed using gravity flow to drain groundwater from areas up the valley to a point at a lower elevation where the tunnel intersects with the surface. The Tehuacan Valley has been shown to have two distinct geological strata containing aquifers. In some areas these strata hold sufficient reserves for the expansion of irrigation agriculture.
